1. Technical Field
The present invention relates to relay technique of communication packets and more specifically to transmission bandwidth control.
2. Description of the Related Art
Recently, streaming technology for real-time delivery of electronic contents, such as video or sound, via a network has become popular. Such streaming via the Internet enables a large number of users to share an identical line, so as to save the cost per bandwidth. There is a requirement for reducing the amount of discarded communication packets and ensuring the quality of service (QoS). One proposed technique provides a relay device with a shaper to smoothen and transfer a large amount of simultaneously transmitted data at a fixed rate (for example, JP H11-346246).
The proposed technique of JP H11-346246 sets a flow condition corresponding to each user or each service as structure definition information, temporarily accumulates each received communication packet into one of queues provided for individual flows, and transfers the communication packet based on a preset shaping condition (e.g., delivery bandwidth or priority). This technique can ensure the preset quality of service for each user or for each service.
The proposed technique of JP H11-346246, however, needs to set a flow for each user or for each service and accordingly has difficulty in dealing with a large number of users or a large number of services. For example, when flows are to be set for several million users, it is practically hard to provide an identical number of several million queues corresponding to the number of the several million users. Even when it is possible to provide several million queues, this requires a storage medium of an enormous storage capacity and has extremely heavy load on sorting received communication packets, thus leading to an unpractical, remarkable cost increase. It is also inefficient to provide queues for all the users including the users of very low activities.
Consequently, in order to address the problem described above, there is a need to provide relay technique that ensures the quality of service, while saving the capacity of a buffer used for queues.